1. Field of the Invention
The present invention relates to bicycle seatpost assemblies and, in particular, to seatpost assemblies utilizing a clamping mechanism to fix the seatpost relative to the seat mast of the bicycle.
2. Prior Art
The seatpost assembly most commonly used on bicycles consists of a split collar mounted to an upper end of the seat mast and having ends which form flanges for receiving a nut and bolt combination. The seatpost used with this collar is substantially tubular in shape and sized to telescope within the seat mast. To adjust the seatpost with respect to the seat mast, the nut and bolt combination is loosened to permit the ends of the split collar to separate, thereby allowing the seatpost to slide relative to the seat mast. When the seatpost and seat which it supports are adjusted to the desired position, the nut and bolt combination is tightened to close the gap in the split collar, thereby clamping the collar against the seatpost and preventing further movement of the seatpost relative to the seat mast and collar.
While this type of seatpost assembly provides an effective means for adjustably mounting a seatpost to the seat mast of a bicycle, it is becoming undesirable from an aesthetic standpoint. With modern multi-speed bicycle designs, it is preferable to provide a streamlined bicycle frame whose various components blend into one another to provide a shape which is pleasing to the eye and at the same time minimizes wind resistance.
Accordingly, it is desirable to provide a seatpost assembly which is contained within the seat mast itself and does not require external collars or other structure which extends laterally outwardly from the seat mast to provide additional surfaces which create wind resistance. At the same time, such a seatpost assembly must be relatively simple to adjust and must provide a positive frictional engagement between the seatpost and seat mast to prevent relative movement during operation.